This invention relates to back flow preventing eductors for mixing of liquid chemicals with water, where the water source must be protected against contamination by backflow.
Eductors are used for mixing liquid chemicals with water. For instance, such devices are used in the custodial arts to formulate small batches of cleaning solutions by mixing a chemical concentrate with water. Water running through the venturi causes the liquid concentrate to be drawn into the venturi, where it is mixed with water and subsequently discharged. In this manner, a dilute solution is formed.
The drawback to mixing devices of this type is the potential for negative water source pressure, or xe2x80x9cback siphoningxe2x80x9d of chemicals into the source of the water supply. When such a drawback occurs, the entire water supply is in jeopardy of contamination. In order to alleviate such a potential hazard, air gap eductors are used to prevent any negative source pressure from drawing chemicals or contaminated water back into the water source. Such devices prevent the drawback of chemicals to the upstream source. Many water regulatory authorities require such devices to be used when diluting and dispensing chemicals in this manner.
Yet such air gap eductors themselves exhibit certain problems. One problem encountered in the use of such devices is the undesired mixture of air along with the chemical concentrate and the water. The introduction of air into the venturi system during operation causes the production of excessive foam. This phenomenon is undesirable, as it prematurely causes the container to be filled with foam rather than liquid. The foam rapidly fills the container and results in an overflow, while the container is only partially filled with the liquid mixture. Such a process is inefficient and causes a loss of both time and product.
Another related problem is the tendency for air gap devices to mist or spit water outwardly of the air gap device. This spray, and the resulting drips are annoying, and over a period of time can cause damage to the wall on which the device is mounted, or puddles on the floor.
These problems with air gap eductors were claimed to have been minimized by the anti-foam, splash-proof venturi device of U.S. Pat. No. 6,240,983. The ""983 patent describes a venturi device with a resilient sleeve check valve between the water inlet and the venturi. The asserted benefits of this sleeve are threefold. First, upon water flow, the sleeve expands to seal off air from flowing into the supplied water and, it is asserted, effectively reduces the amount of foam produced at the outlet of the venturi. The second claimed asserted benefit of the ""983 patent is the elimination of leakage previously experienced in some open air gap eductors. The sleeve used in this device acts as a barrier and confines all fluids to the interior of the venturi device. The last asserted benefit of the ""983 patent is that the sleeve insert acts to seal the water flow passage and thus opens the venturi to outside air, providing a siphon-break preventing backflow when water is not flowing through it.
Despite the improvements that the ""983 device is alleged to have made to venturi-type eductors, there are difficulties with that device. Sleeve wear and degradation occur over time periods shorter than desired and new parts are required. Degradation may be a result of large portions of the sleeve being forced through the air gaps or ports during water flow. As the sleeve is bulged outwardly and comes into contact with the rough edges of the housing, that relative motion results in abrasion to the sleeve, which leads to undue sleeve wear. Such degradation results in adverse performance and eventually complete failure of the system.
Debris in the water flow passage defined between the sleeve and the internal rigid barrel can prevent the sleeve from fully sealing on the barrel where water flow ceases. This can leave passages open to the undesirable contaminating backflow. Thus, debris in the water flow passage is significantly problematical.
Another problem with devices such as in the ""983 patent is the tortuous water path. In that device, the water must flow into a rigid support barrel, make a right turn outwardly through ports toward the resilient sleeve, then make another right turn between the expanded sleeve and support barrel. The turbulence caused by this arrangement restricts the water flow capacity of the device.
Another problem with the ""983 patented device is in the manner of the connection of the lower venturi section to the upper air gap/breaker section. These units are joined by hose end threads, making it too easy for the venturi to be disconnected and connected directly to a water source, but without the breaker. This eliminates the function and safety of the breaker, defeating the purpose of the device disclosed.
Moreover, this type of coupling makes the angular orientation of the backflow breaker and of the venturi section or rigid coupling. This may make alignment of the chemical inlet with the portions of the dispensing system a difficult, cumbersome task. Also, twisting of the outlet tube at the end of the venturi is restricted.
A preferred embodiment of the invention includes a backflow preventing eductor having an improved anti-backflow housing, a venturi section or housing, an improved resilient sleeve for sealing the system against backflow, an improved sleeve support barrel for directing water flow, and improved structure interconnecting the anti-backflow housing with the venturi housing.
More specifically, the improved anti-backflow housing is provided with elongated air vents in which cross-bars effectively define smaller vents or windows which are less susceptible for intrusion by the expanded sleeve which would prematurely wear the sleeve.
The improved resilient sleeve is contoured in thickness, tapering toward its distal end to a thinner wall section. The thinner section at the distal end is more compliant, providing a better seal around any debris in the water passage, and accommodating increased water flow for any given pressure over that provided by prior uniformly thick sleeves. The rigid sleeve support barrel has water outlet ports directed toward the sleeve. These ports are extended into the flange of the barrel, thus providing a straighter, less turbulent water path resulting in an increased flow, for any given size of barrel and openings, over the prior device.
A transition area in the anti-backflow housing supports the thinner distal end of the expanded sleeve at the lower end when the expanded sleeve seals against the housing. This, too, reduces wear of the sleeve on that seal where water is flowing in the sleeve.
Finally, the anti-backflow housing is rotatably secured together with the venturi section by a flange and seal so the venturi section can be rotated with respect to the anti-backflow, facilitating orientation of the chemical inlet and twisting of the outlet tube.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.